The present invention relates to ultrasonic systems, and more particularly, to methods of and systems for generating high power ultrasonic sound energy and introducing the ultrasonic sound energy into fluid media for the purpose of cleaning and/or liquid processing
For years, ultrasonic energy has been used in manufacturing and processing plants to clean and/or otherwise process objects within liquids. It is well known that objects may be efficiently cleaned by immersion in an aqueous solution and subsequent application of ultrasonic energy to the solution. Prior art ultrasound transducers include resonator components that are typically constructed of materials such as piezoelectrics, ceramics, or magnetostrictives (aluminum and iron alloys or nickel and iron alloys). These resonator components spatially oscillate at the frequency of an applied stimulating signal. The transducers are mechanically coupled to a tank containing a liquid that is formulated to clean or process the object of interest. The amount of liquid is adjusted to partially or completely cover the object in the tank, depending upon the particular application. When the transducers are stimulated to spatially oscillate, they transmit ultrasound into the liquid, and hence to the object. The interaction between the ultrasound-energized liquid and the object create the desired cleaning or processing action.
One type of prior art ultrasound transducer includes one or more resonator components compressed between a front plate and a back plate. In these types of ultrasound transducers, the back plate is typically made from a high-density material such as steel. Although they provide rugged, reliable service, one disadvantage of such high-density back plates is a relatively narrow-band frequency response from the transducer. The prior art resonator components are typically cylindrically symmetrical about a central axis. Although such symmetrical resonators are relatively easy to manufacture because the symmetry lends itself to common fabrication processes. However, symmetrical resonators also tend to produce a relatively narrow-band frequency response.
Prior art resonator components are typically “silvered,” i.e., a conductive material such as silver, tin, gold, solder, etc., is applied to one or more surfaces of the resonator component to create an electrical contact. This silvered contacts primary purpose is to provide a uniform electrical charge across the surface of the resonator. After the silvering process, the resonator goes through a “poling” process that aligns the dipoles in the internal structure of the piezoelectric resonator. One disadvantageous side effect of this process is the introduction some small dimensional deformations. A second disadvantage of prior art resonators is the non-uniformity in the thickness of the silver coating itself, caused by the method of silk-screening the silvered coating on, which is inherently non-uniform. Such deformations and non-uniform thickness effect the flatness of the resonator surface and therefore the mechanical coupling and final performance of the transducer stack.